Practice Arena

Python Coding
Challenges

Write real Python in the browser. Instant feedback. From beginner to expert.

925 challenges 556 easy 323 medium 46 hard

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All Python Basics Strings & Text Lists & Arrays Dicts & Sets Functions & Closures OOP & Classes Data Structures & Algorithms Advanced Python Iterators & Generators Decorators & Context Managers Error Handling & Exceptions Regular Expressions Math & Number Theory Bit Manipulation Dynamic Programming Trees & Binary Trees Graphs & Graph Algorithms Recursion & Backtracking Greedy Algorithms Binary Search Two Pointers & Sliding Window Stacks & Queues Heaps & Priority Queues Linked Lists Matrix & 2D Arrays Datetime & Time Calculations Data Formats & Parsing SQL & SQLite Numpy & Vectorized Computing Cryptography & Hashing

Lists & Arrays easy

Majority Element Finder

Implement a function that returns the majority element in a list, which appears more than half the time.

majority frequency arrays

Lists & Arrays easy

Difference of Two Lists

Write a function that returns items in list a that are not in list b, preserving order and duplicates.

lists difference counting

Lists & Arrays easy

Counting Sort

Implement the counting sort algorithm to sort a list of non-negative integers in O(n + k) time.

sorting counting arrays

Lists & Arrays medium

Count Smaller Numbers

Given an integer list, return for each position how many later elements are smaller than it.

arrays counting merge-sort

Lists & Arrays easy

Count Adjacent Pairs

Given a list of integers and a target, count adjacent pairs whose sum equals the target.

pairs sum adjacent

Lists & Arrays easy

Intersection two lists length

Return the number of distinct elements that appear in both input lists.

lists sets intersection

Showing 1–6 of 6 challenges · Lists & Arrays

Lists & Arrays — Python coding challenges

What you will find here

This page lists lists & arrays challenges — real Python problems you solve in the browser IDE with instant test feedback. Each challenge includes a clear brief, starter code, and automated checks.

Challenges vs tutorials and quizzes

Challenges test what you can build under constraints. For guided teaching, use our Python tutorials. For quick checks, try quizzes or copy snippets from code samples.